A pressure distribution detector has widely been used in various fields such as seat pressure detection of vehicles such as a car, welfare devices such as a bed, medical or sports devices for measuring weight distribution during walking, artificial skin of robots, and man-machine interfaces of a computer or game instrument.
As a device for measuring a pressure and displacement amount, there is known one using a differential transformer as disclosed in Patent Document 1. This device adopts a system that uses a core and a differential coil to detect the relative change amount between them. However, the core and the differential coil each have a certain degree of thickness, so that it is difficult to form the mechanism in a thin sheet-like shape. Accordingly, it is difficult to realize a sheet-like pressure measurement device by utilizing the above system.
As a pressure distribution detector which is formed into a thin sheet-like shape, there can be exemplified one using a pressure-sensitive rubber as disclosed in Patent Document 2 and one using electrostatic coupling as disclosed in Patent Document 3. These pressure distribution detectors have comparatively high impedance, so that they are susceptible to noise, and, therefore, it is difficult to increase the size of the detection surface thereof.
As a device that can measure the pressure distribution by using electromagnetic coupling caused by coils, there can be exemplified one disclosed in Patent Document 4 proposed by the present inventor. This is a system that provides a cushion material between a drive coil to which an oscillator is connected and a detection coil to which a detection circuit is connected and measures a change in the electromagnetic coupling caused by a change in the distance between the drive coil and the detection coil. The system of Patent Document 4 using the electromagnetic coupling caused by coils has a high tolerance for noise because of low impedance, and can be formed into a sheet-like shape, and the size of the detection surface can be larger.
Patent Document 1: Japanese Patent Application Kokai Publication No. Hei 09-113203
Patent Document 2: Japanese Patent Application Kokai Publication No. Sho 57-100331
Patent Document 3: Japanese Patent Application Kokai Publication No. Sho 62-226030
Patent Document 4: Japanese Patent Application Kokai Publication No. 2005-156474